1. Field of the Invention
The present invention relates to an image processing apparatus associated with encoding/decoding processing of image data.
2. Related Background Art
As conventional encoding schemes for digital motion images, the following two schemes are known:
(1) an intraframe/intrafield (intraframe) encoding scheme of encoding image data in units of frames/fields; and PA1 (2) an interframe/interfield (interframe) encoding scheme of encoding differences between frames/fields.
In the intraframe/intrafield encoding scheme, since each frame/field is encoded independently, edit processing can be easily performed in units of frames/fields.
In addition, the encoding and decoding algorithms are simple and hence can be easily realized by hardware and software. However, one drawback of this scheme is that the compression ratio is not very high.
In the interframe/interfield encoding scheme, a high compression ratio can be realized as compared with the intraframe/intrafield encoding scheme. However, edit processing performed in units of frames is complicated, and the hardware for coding and decoding operations is complicated.
In a conventional apparatus, in changing the encoding scheme, encoded data is completely decoded first, and the decoded data is then encoded again by a desired encoding scheme.
In such a conventional apparatus, in switching the encoding scheme, two types of encoders, i.e., an intraframe/intrafield encoder and an interframe/interfield encoder, are required. Consequently, the circuit size is large, and the cost is high. Furthermore, encoding processing is complicated.
In addition, quantization errors occur in the process of converting encoded data into completely decoded image data, resulting in a deterioration in image quality.